docs: def dump_pmean(self, filename):
          """ Dump parameter means (``fit.pmean``) into file ``filename``.
  
          ``fit.dump_pmean(filename)`` saves the means of the best-fit
          parameter values (``fit.pmean``) from a ``nonlinear_fit`` called
          ``fit``. These values are recovered using
          ``p0 = nonlinear_fit.load_parameters(filename)``
          where ``p0``'s layout is the same as ``fit.pmean``. The saved
          values can be used to initialize a later fit (``nonlinear_fit``
          parameter ``p0``).
          """
          warnings.warn(
              "nonlinear_fit.dump_pmean deprecated; use pickle.dump instead",
              DeprecationWarning,
              )
          with open(filename, "wb") as f:
              if self.p0.shape is not None:
                  pickle.dump(numpy.array(self.pmean), f)
              else:
                  pickle.dump(collections.OrderedDict(self.pmean), f)